1. Technical Field
The present invention relates to a technology for correcting light intensity (power) of an electro optical element such as a light emitting element or the like.
2. Related Art
In an electro optical device in which many electro optical elements are arranged, there is a problem in that variation of light intensity caused by the property of each electro optical element and the error (difference from the design value or variation between each element) of the property of an active element for driving the electro optical element. In JP-A-2002-144634 (hereinafter, referred to as Patent Document 1) and JP-A-2005-081696 (hereinafter, referred to as Patent Document 2), a technique is disclosed for eliminating the variation of each light intensity by correcting the electric energy supplied to each light emitting element. For example, when the light intensity of each light emitting element in the case of no correction varies in the range of Δ0 as shown in FIG. 20, the light intensities of all of the light emitting elements are adjusted to a predetermined value Pave at the time TA when the electro optical device is started to be used by increasing the electric energy supplied to a light emitting element whose light intensity is low (for example, the light emitting element E1 having light intensity P0_a) as compared with the electric energy of the light emitting element (for example, the light emitting element having light intensity P0_b) E2 whose light intensity is high.
Incidentally, the electro optical element (in particular, the light emitting element such as an organic light emitting diode) is deteriorated with time caused by supply of electric energy. Deterioration of the electro optical element is facilitated as high energy is supplied thereto. Accordingly, when light intensity is corrected as in FIG. 20, the light emitting element E1 whose light intensity is low in the case of no correction (that is, light emitting device in which electrical energy is corrected in the increase direction) is rapidly deteriorated than the light emitting element E2 whose light intensity is high in the case of no correction. Accordingly, in the structure described in Patent Document 1 and Patent Document 2, there is a problem in that the error of the property of each light emitting element is increased with time. For example, although the light intensity of all of the light emitting elements is equalized at the time TA as in FIG. 20, the difference of the light intensity of the light emitting elements E1 and E2 is increased to Δ1 at the time TB when a predetermined time has passed form the time TA. Further, there is a case in that the difference becomes larger than the range Δ0 of the light intensity in the case where no electric energy is corrected.